1. Field of the Invention
The present invention generally relates to pharmaceutical-grade ferric citrate, and particularly to a pharmaceutical composition, food comprising pharmaceutical-grade ferric citrate and a method for manufacturing pharmaceutical-grade ferric citrate.
2. Description of Related Art
U.S. Pat. No. 5,753,706 ('706) discloses that a ferric citrate compound can be used to control phosphate metabolism and prevent metabolic acidosis in patients. A ferric citrate compound is used with patients suffering from renal failure associated with hyperphosphatemia or patients predisposed to development of a hyperphosphatemic condition. Ferric citrate is used as a food supplement, too. According to the '706 patent, ferric citrate was purchased from the Sigma-Aldrich Company, contained 16.5%-18.5% of Iron(III) and had a formula of FeC6H5O7 and a formula weight of 244.9. Ferric citrate is garnet-red, transparent scales or pale-brown powder, odorless and slightly ferruginous tasting. Ferric citrate is slowly but completely soluble in cold water and readily soluble in hot water but diminishes in solubility with age (The Merck Index, 12th Edition, page 4068).
Although ferric citrate is commercially available, the purchased ferric citrate is a combination of iron and citric acid of indefinite composition (The Merck Index, 12th Edition, page 4068) probably because of the difficulty encountered in its preparation. People knowledgeable in the art understand and necessarily accept that commercially available ferric citrate contains different molar ratios of iron and citric acid and also contains different amounts of hydrate.